The present invention relates to an aircraft engine exhaust nozzle system, and more specifically, to an aircraft engine exhaust nozzle system reducing jet noise by acoustic shielding.
Conventional aircraft typically include propulsion engines, which are under the wing or tail surfaces. FIG. 1 illustrates an aircraft including a conventional engine exhaust nozzle system. As shown in FIG. 1, the aircraft 100 includes a fuselage 101, wings 102, and a propulsion engine system 103. The propulsion engine system 103 is attached underneath the wing 102 by a pylon structure 107. Each propulsion engine system 103 includes an engine 106 housed in a nacelle 104 and having an inlet 105 and a nozzle system 150. The nozzle system 150 releases a jet exhaust from the engine into the atmosphere. Primary component noise sources from the engine system 103 include the noise associated with each of the fan, compressor, turbine, combustor, and that noise associated with the high velocity jet exhaust flow. There are many methods for reducing the various noise sources from the aircraft 100 including those noise sources from the engine system 103. One method that has the potential of significant noise reduction includes the use of the aircraft itself as an acoustic shield for the noise sources associated with the engines 106. This approach requires a new configuration of aircraft with the engines installed on the upper surface of the wing 102, fuselage 101, or an aircraft that has a hybrid wing and fuselage. Of the engine noise sources, the jet exhaust noise source is a particular challenge due to the fact that the noise sources are in the exhaust flow itself and therefore originate throughout the jet exhaust flow as many as ten engine diameters downstream of the nozzle system 150 exit plane.
Therefore, it is desirable to have an improved aircraft nozzle system that is capable of much more noise reduction when installed on the upper surface of the aircraft.